CAIRO – The installation of military men into powerful new roles in the Egyptian government on Saturday reflected a martial style of rule unbroken in Egypt since Gamal Abdel Nasser and his young officers toppled the monarchy in 1952.

The newly designated vice president, Omar Suleiman, 74, has headed Egypt’s intelligence service for 18 years. Along with a new prime minister who is a former air force commander, Suleiman is first among a troika of leaders on whom President Hosni Mubarak is relying in what appears to be an attempt to secure the regime, if not his presidency, after days of protests aimed at his ouster.

U.S. officials have long viewed Suleiman as a likely transitional leader, at minimum, after Mubarak left office. In a classified cable released by the anti-secrecy group WikiLeaks, a 2007 State Department assessment described Suleiman as a “rock-solid” loyalist to Mubarak who was being groomed, even then, for a more public role.

With army tanks dispatched into the streets, where soldiers sought to calm angry protesters, the changes on Saturday affirmed the pivotal role of Egypt’s military and intelligence services in a country whose army has long held citizens’ respect, even if its commanders are disliked.

Suleiman is known as a close and trusted adviser to Mubarak, as is Ahmed Shafiq, 69, the newly designated prime minister. Field Marshal Mohammed Hussein Tantawi, 75, who remains in place as the top military commander, isn’t seen as a possible successor but likely would be an important figure in ensuring the military’s loyalty to a new government.

It was a combination unlikely to appease demonstrators who have been demanding an end to Mubarak’s rule entirely.

“I feel today is a disappointment,” said Emad Abdel Halim, 31, upon learning Saturday that Mubarak had chosen Suleiman as vice president, the successor’s post held by Mubarak when he inherited power from Anwar Sadat. “We don’t want him as our next president.”

Despite the warm greetings given to demonstrators by soldiers in the street, there were no signs that the generals had abandoned Mubarak, himself a former air force commander. Analysts said it appeared likely that the soldiers had been instructed to avoid the kinds of violent clashes mounted by police who had confronted the protesters with tear gas, rubber bullets and live ammunition.

“I think Mubarak has huge confidence in Tantawi’s ability to keep the army under control,” said a retired U.S. military official familiar with Egypt.

But there was some speculation that the military’s top brass was still sorting out how to deal with the demonstrators and whether to continue to back Mubarak amid unprecedented calls for his ouster.

“What I’m feeling is there is a conflict inside the Egyptian army, and they did not yet find a solution as to how to sort out what’s happened in this country. I believe that some of them are with Mubarak and some are against,” said Yousef Zaki, a former leader of Egypt’s historic Wafd party. “There is no clear direction.”

Along with Tantawi, another top military figure is Lt. Gen. Sami Enan, 62, the army chief of staff, who in his few years in the position has developed good relations with his military counterparts in Washington.

Suleiman is perhaps better recognized in foreign capitals than in Cairo. For much of his time as Egypt’s intelligence chief, he worked behind the scenes with the Central Intelligence Agency and intelligence services across the Middle East. In recent years, he assumed a more high-profile role, traveling routinely to Israel to discuss the peace process and attempting to broker a rapprochement between the rival Palestinian factions, Hamas and Fatah.

The tanks deployed throughout Egypt’s major cities offered a reminder of the key role that the military has played in the country’s history since the 1952 revolution. Among Egyptians who have felt victimized by domestic security forces, the army is seen as a protector, not only from potential threats beyond Egypt’s border but also from the government itself.

“The military and the people we are one,” demonstrators chanted as protesters rode aboard armored military vehicles through the streets of Cairo on Saturday.

With an estimated 480,000 men in arms, Egypt’s military is the 10th largest in the world. Yet with a peace treaty with Israel for more than three decades, Egypt hasn’t had much to do outside its borders, and the military has as a result focused its energies internally.

“They’re not interested in fighting wars,” the retired American military official said. “They’re interested in the stability of the country.”